/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.apis.graphics;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.BitmapFactory.Options;
import android.view.View;

import java.io.ByteArrayOutputStream;

/**
 * PurgeableBitmapView works with PurgeableBitmap to demonstrate the effects of
 * setting Bitmaps as being purgeable.
 * 
 * PurgeableBitmapView decodes an encoded bitstream to a Bitmap each time
 * update() is invoked(), and its onDraw() draws the Bitmap and a number to
 * screen. The number is used to indicate the number of Bitmaps that has been
 * decoded.
 */
public class PurgeableBitmapView extends View {
	private final byte[] bitstream;

	private Bitmap mBitmap;
	private final int mArraySize = 200;
	private final Bitmap[] mBitmapArray = new Bitmap[mArraySize];
	private final Options mOptions = new Options();
	private static final int WIDTH = 150;
	private static final int HEIGHT = 450;
	private static final int STRIDE = 320; // must be >= WIDTH
	private int mDecodingCount = 0;
	private final Paint mPaint = new Paint();
	private final int textSize = 32;
	private static int delay = 100;

	public PurgeableBitmapView(Context context, boolean isPurgeable) {
		super(context);
		setFocusable(true);
		mOptions.inPurgeable = isPurgeable;

		int[] colors = createColors();
		Bitmap src = Bitmap.createBitmap(colors, 0, STRIDE, WIDTH, HEIGHT,
				Bitmap.Config.ARGB_8888);
		bitstream = generateBitstream(src, Bitmap.CompressFormat.JPEG, 80);

		mPaint.setTextSize(textSize);
		mPaint.setColor(Color.GRAY);
	}

	private int[] createColors() {
		int[] colors = new int[STRIDE * HEIGHT];
		for (int y = 0; y < HEIGHT; y++) {
			for (int x = 0; x < WIDTH; x++) {
				int r = x * 255 / (WIDTH - 1);
				int g = y * 255 / (HEIGHT - 1);
				int b = 255 - Math.min(r, g);
				int a = Math.max(r, g);
				colors[y * STRIDE + x] = (a << 24) | (r << 16) | (g << 8) | b;
			}
		}
		return colors;
	}

	public int update(PurgeableBitmap.RefreshHandler handler) {
		try {
			mBitmapArray[mDecodingCount] = BitmapFactory.decodeByteArray(
					bitstream, 0, bitstream.length, mOptions);
			mBitmap = mBitmapArray[mDecodingCount];
			mDecodingCount++;
			if (mDecodingCount < mArraySize) {
				handler.sleep(delay);
				return 0;
			} else {
				return -mDecodingCount;
			}

		} catch (OutOfMemoryError error) {
			for (int i = 0; i < mDecodingCount; i++) {
				mBitmapArray[i].recycle();
			}
			return mDecodingCount + 1;
		}
	}

	@Override
	protected void onDraw(Canvas canvas) {
		canvas.drawColor(Color.WHITE);
		canvas.drawBitmap(mBitmap, 0, 0, null);
		canvas.drawText(String.valueOf(mDecodingCount), WIDTH / 2 - 20,
				HEIGHT / 2, mPaint);
	}

	private byte[] generateBitstream(Bitmap src, Bitmap.CompressFormat format,
			int quality) {
		ByteArrayOutputStream os = new ByteArrayOutputStream();
		src.compress(format, quality, os);
		return os.toByteArray();
	}

}
